The present invention relates generally to a class of medical devices commonly referred to as oral airways and supraglottic airways which are inserted through a patient""s mouth and into the patient""s pharynx while the patient is undergoing general anesthesia or is undergoing respiratory treatment such as is carried out with cardiopulmonary resuscitation. More specifically, the present invention is directed to a perilaryngeal oral airway and perilaryngeal supraglottic airway which is capable of acting as an endotracheal tube guide and which seats deep in a patient""s hypopharynx to prevent the soft tissue of the glottis and epiglottis from obstructing the airway.
Oral airways were introduced into the practice of anesthesia and cardiopulmonary resuscitation several decades ago for two basic purposes. First, they prevent the patient""s biting down on and occlusion of a previously placed oral endotracheal tube. Second, and most important, oral airways help to provide a patent airway that allows positive pressure ventilation to be carried out by the practitioner. More recently, some oral airways have been developed to facilitate blind (not visually directed) placement of an endotracheal tube.
For most patients, mask ventilation is carried out successfully by insertion of an oral airway and by a variety of physical adjustments, such as extension of the patient""s neck and elevation of the patient""s jaw. However, in some patients, no matter what physical adjustments are made or the particular oral airway which is inserted, mask ventilation cannot be successfully achieved. Such cases are literally life-threatening as hypoxemia and death can quickly ensue if the patient""s blood is deprived of oxygen due to a lack of ventilation.
When mask ventilation (even with the use of an oral airway) cannot be carried out, there are multiple mechanisms responsible. Most significantly, soft tissue structures in the hypopharynx (the area between where conventional oral airways end and the glottis opens into the trachea) collapse inwardly and obstruct airflow. This collapse occurs from both an antero-posterior direction, as well as from the sides of the hypopharynx. Unfortunately, all oral airways which have been introduced into practice to date end bluntly well above the epiglottis (the cartilaginous structure just above the glottis or laryngeal opening) and glottis and thus place patients at risk for significant airway obstruction. Another mechanism of airway obstruction which occurs while using oral airways is the patient having large lips covering the outside opening of the oral airway with subsequent inadequate airflow through the nasal passages (due to the solid posterior wall of the airway limiting passage of air into the airway at the level of the nasopharynx).
Additionally, most known oral airways are comprised of a hard plastic material throughout their length with no variation in softness between one end of the oral airway and the opposite end. As a result, the distal end (i.e., the end which first enters the mouth and passes down into the pharynx of the patient) often bruises or otherwise damages soft mucosal surfaces of the patient during insertion or once the oral airway has been seated in place.
Representative prior art airways include Baildon, U.S. Pat. No. 4,919,126, which discloses an oral airway formed of plastic which includes an air passageway extending longitudinally through the airway. The distal end has a projecting solid anterior portion which serves as an xe2x80x9cepiglottis elevator.xe2x80x9d As such, the oral airway is blunt-shaped in configuration and ends well above the glottis. For this reason, the Baildon oral airway suffers from the problems discussed above in that it fails to provide any structure to prevent the collapse of soft tissue structures in the hypopharynx.
Berman, U.S. Pat. Nos. 4,054,135 and 4,067,331, relate to an intubating pharyngeal airway having a side access for passage of an endotracheal tube. The airway includes a blunt end on the anteriorly extending wall which is designed to fit into the vallecula (area between the epiglottis and tongue). Accordingly, the devices disclosed in both of Berman""s patents are similar to the device of Baildon in that they can detrimentally allow soft tissue structures to invaginate inward and thereby occlude the passage of air.
Moses, U.S. Pat. No. 3,908,665, discloses an oro-pharyngeal airway wherein the outer diameter of the body portion progressively increases from the end closest to the mouth to the opposite end thereof so as to relieve any obstruction to the flow of air by the base of the tongue falling back on the posterior pharyngeal wall. However, the airway of Moses likewise suffers from the problems discussed in detail above in that the blunt-shaped end terminates well above the glottis, thereby allowing possible soft tissue obstruction to occur.
Augustine, U.S. Pat. No. 5,203,320, discloses a tracheal intubation guide which similarly seats above the glottis. Moreover, the device of Augustine functions as a guide for placing an endotracheal tube in a xe2x80x9cblindxe2x80x9d manner and is neither designed for nor could it possibly function to allow mask ventilation to be carried out.
In addition, for some patients it is important to use an airway device which provides a seal within the patient""s airway (trachea, oro- or hypopharynx) in order to better allow positive pressure ventilation to be accomplished. These airways are referred to herein as supraglottic airways. Traditionally, this has been achieved by using an endotracheal tube passed between a patient""s vocal cords. In an effort to avoid the deleterious effects of tracheal intubation (e.g., bronchospasm, dental injury and cardiovascular stimulation), the laryngeal mask airway (xe2x80x9cLMAxe2x80x9d) has been introduced into clinical practice. The LMA is illustrated and described in Brain, U.S. Pat. No. 4,509,514. While providing a seal with which to administer positive pressure ventilation, there are several potential problems when using an LMA. First, the device is easily malpositioned so that ventilation is not possible, for example, by virtue of the epiglottis bending back over the glottis and thereby obstructing air flow. Second, by directly covering the glottic aperture, trauma to the glottic structures (arrhytenoid cartilages, vocal cords) can occur. In addition, the cost of this product (over $200) becomes a factor when limitations to reuse occur due to physical damage of the device or accidental loss. Third, as a reusable product, the hazard of cross-contamination from one patient to another cannot be completely eliminated.
Because of the above-limitations of the LMA, a cuffed oro-pharyngeal airway has been introduced into clinical practice. Greenberg, U.S. Pat. No. 5,443,063, describes such a device as an oro-pharyngeal cuff placed over a conventional oral airway. However, this device has several significant limitations which prevent it from functioning adequately. First, the airway suffers from the problems of those previously discussed in that it ends well above the glottis, thereby allowing soft tissue obstruction to impair the flow of oxygen to the lungs. Second, with the cuff placed so far proximally in the oro-pharynx, the device tends to push itself out of the patient""s mouth, thereby requiring that the device be secured in place by means of a strap placed around the patient""s head. Finally, the cuff is positioned so far proximally in the patient""s airway that it often allows leakage of oxygen and anesthetic gases around the cuff, thereby preventing the formation of an air-tight seal. This, of course, makes positive pressure ventilation impossible in those patients.
Several oral airways, including those described in the patents to Berman and Augustine, have been introduced into clinical practice in an effort to provide a means to accomplish blind intubation of a patient""s trachea with an endotracheal tube (or to facilitate fiberoptic intubation). These devices end well above the glottic opening and thus function poorly in terms of reliably directing the end of an endotracheal tube into the glottis with blind passage. As a result, the hard distal end of the endotracheal tube may be directed against the structures which surround the glottic opening (arytenoid, cuneiform and corniculate cartilages, epiglottis, aryepiglottic folds) and cause damage to these structures or their soft tissue surfaces. Further, that damage may result in hemorrhage which obscures vision if subsequent placement of the endotracheal tube by means of a fiberoptic device is attempted. Other prior art has attempted to better direct an endotracheal tube into the glottis by having walls which surround and thus engage the arytenoid cartilages or which have projections which physically enter in between those cartilages. Representative are Patil, U.S. Pat. No. 5,720,275; Krxc3xcger, U.S. Pat. No. 4,612,927; and Williams, U.S. Pat. No. 4,338,930. However, these structures have hard advancing surfaces which can likewise cause trauma.
Recently, a version of the LMA which is meant to facilitate blind intubation with an endotracheal tube has been introduced into clinical use which attempts to surmount the problems of a misguided endotracheal tube causing trauma to perilaryngeal and glottic structures. This LMA is described in Brain, U.S. Pat. No. 5,896,858. However, in addition to sharing the above discussed problems common to all LMA""s, this device relies on precise positioning so that a movable flap raises an obstructing epiglottis out of the way of an advancing endotracheal tube. Because the attached flap resides within the body of the LMA it does not physically contact the epiglottis upon insertion, but rather the advancing endotracheal tube pushes the flap up against the epiglottis to move it out of the way and thus open the glottic aperture for the endotracheal tube to enter. Perfect alignment of the recessed flap with the epiglottis is thus necessary to reliably accomplish blind placement of the endotracheal tube. However, LMA""s occupy a somewhat variable and inconsistent position within the hypopharynx in relation to the precise anatomic location of the glottis (due to anatomic variability among patients as well as the distensible nature of the proximal epiglottis and hypopharynx where it resides). As a result, blind intubation with an endotracheal tube with this device can also result in tissue trauma by virtue of its advancing end being misdirected.
The importance of monitoring and maintaining core body temperature when patients undergo general anesthesia is now being more clearly recognized. Significant reductions in body temperature (which are the common and usual course following induction of general anesthesia) in patients undergoing surgery are associated with an increased incidence of cardiac morbidity, increased rates of wound infection, impaired wound healing and alterations in blood coagulation status. In addition, although rare, a patient undergoing general anesthesia may have a sudden and dramatic rise in body temperature due to an abnormal acceleration of metabolic rate in a condition termed maligmant hyperthermia. This is a life-threatening syndrom which requires prompt recognition and treatment if a patient is to survive, and the rise in body temperature is one of the hallmarks used to diagnose its occurrence. Further, in order to reliably measure body temperature, a xe2x80x9ccorexe2x80x9d temperature must be used. As such, a thermistor or thermal couple temperature probe must be in contact with a deep visceral cavity (e.g., urinary bladder, esophagus), blood, or an internal mucosal surface (e.g., hypopharynx, nasopharynx) which reflects inner body temperature as opposed to surface temperature of the patient. No supraglottic airway or oral airway which is currently in use provides measurement of core temperature by a temperature sensor incorporated into that device.
Supraglottic airways are sometimes used in anesthetized patients undergoing surgery within the oral cavity or on the head and neck. As such, the presence of the breathing tube can be a physical impediment to the operating surgeon. Known oral airways are too rigid to allow the airway to be moved from the surgical field. Further, a version of the LMA which is made using a flexible reinforced breathing channel suffers from the limitations common to LMAs discussed above.
The present invention is intended to overcome one or more of the problems discussed above.
One aspect of the present invention provides an oral airway wherein the distal end portion thereof is extended and shaped in order to seat deep in the hypopharynx and to actually surround the epiglottis and glottis (thus the name xe2x80x9cperilaryngeal oral airwayxe2x80x9d). By extending around the epiglottis and the glottis, the perilaryngeal oral airway of the present invention is able to physically hold the patient""s soft tissue in the hypopharynx away from the glottic opening.
In particular, the oral airway includes a curved hollow, tubular longitudinally extending body member, the body member having a distal end portion for insertion into the mouth and pharynx of a patient and a proximal end portion for location at the mouth of the patient, wherein the distal end portion of the body member is extended and shaped so as to be operative to seat deep in the patient""s hypopharynx and terminate just above or surround the patient""s epiglottis and glottis, thereby to hold the patient""s soft tissue away from the patient""s air channel opening.
In one embodiment, the distal end portion of the body member is divided so as to form a pair of elongated extension walls which are operative to seat deep in the patient""s hypopharynx and surround the patient""s epiglottis and glottis, thereby to hold the patient""s soft tissue away from the patient""s air channel opening. More specifically, an opening, which may be rectangular, trapezoidal, U-shaped or V-shaped is formed in the distal end portion as a result of the division or separation of the distal end portion of the body member so as to form the two elongated extension walls and into which the epiglottis and glottis are positioned. The elongated extension walls at the distal end portion expand outward laterally to allow sufficient space in which to accommodate the epiglottis and glottis within the openings. The extreme distal ends of the elongated extension walls may be angled inward slightly, thereby providing a smooth contour.
Another embodiment of the present invention further provides elongated lateral extension walls which are relatively flexible and soft so that there is at least some xe2x80x9cgivexe2x80x9d as the oral airway is inserted into the patient. The particular firmness of the walls must strike a balance between the need to hold the hypopharyngeal and perilaryngeal structures away from the glottis, the need to move the soft tonsillar and oro-pharyngeal structures to the side as the oral airway is inserted, and the desire for the oral airway to be able to bend inwardly when inserted through the back of the patient""s mouth. Likewise, the body member of the oral airway is of sufficient softness and pliability to bend during insertion and to accommodate different angles once successfully inserted into the patient, since a given patient""s head and neck may be slightly flexed or extended to provide optimal positioning for mask ventilation. The most proximal end portion of the oral airway is much harder than the distal end portion in order to prevent occlusion by the patient biting down thereon.
In a further embodiment, rather than dividing the distal end portion of the body member so as to form a pair of elongated extension walls, the posterior wall of the distal end portion is filled in. In this way, the posterior wall of the distal end portion serves to better hold tissue away from the larynx. Likewise, the anteriorly placed opening which is V-shaped, U-shaped, rectangular or trapezoidal, may be made smaller in order to cover and hold away the epiglottis while still allowing air passage into the glottis. Alternatively, a grate may cover the opening to keep the epiglottis and other tissue out of the opening.
Further, in any of the above-described embodiments, holes or fenestrations may be formed through the distal anterior wall of the body member of the oral airway in order to provide ventilation should the distal end portion be positioned directly over the glottic opening of the patient, as might occur if the practitioner has selected too large of an oral airway for a particular patient, or the patient has an abnormally high (rostrally) placed glottic opening. Moreover, holes may be formed through the anterior surface of the elongated extension walls and which function to allow ventilation should the oral airway be situated at an abnormal angle such that one of the elongated extension walls covers the glottis. Still further, additional air holes or fenestrations may be formed through the posterior wall of the body member of the oral airway at the region of curvature which is adapted to be positioned at the back of the oropharynx and which allow passage of air through the nasal passages of the patient and into the oral airway per se. Of course, the holes can be dispensed with entirely if desired.
According to a still further embodiment, the oral airway includes an inflatable cuff positioned just above the distally placed notch. Accordingly, the distal end of the perilaryngeal oral airway is easily seated around the larynx, thereby holding the soft tissues away from the glottic aperture, and the more distally positioned cuff is located within the hypopharynx and thereby allows the oral airway to be held in place without external means and avoids the airway leakage which can occur at the base of the tonsillar pillars and soft palate when using the conventional cuffed oro-pharyngeal airway.
Also contemplated is a method of administering anesthesia or respiratory treatment using an anesthesia or respiratory circuit to a patient using the perilaryngeal oral airway of the present invention.
Another aspect of the present invention is an oral airway referred to as a grated oral airway or grated perilaryngeal oral airway includes an elongate tubular member having a distal and a proximal end with an enlarged wedge-shaped housing at the distal end. The wedge-shaped housing is for insertion into the mouth and pharynx of a patient with the proximal end of the tubular member extending from the mouth of the patient. The wedge-shaped housing has anterior and posterior walls forming an enlarged proximal portion tapering to a smaller distal portion with a leading opening separating the anterior and posterior walls at the distal end of the housing. A grate covers the leading opening. Sidewalls extend between the anterior and posterior walls and the wedge-shaped housing is configured so that the sidewalls abut the aryepiglottic folds as the wedge-shaped housing is inserted in to the hypopharynx of a patient to arrest insertion of the wedge-shaped housing and seat the wedge-shaped housing with the leading opening adjacent to the glottis. The grate is inclined between the posterior and anterior walls so that as a patient""s epiglottis is engaged by the grate during insertion of the wedge-shaped housing into the hypopharynx, the epiglottis slides up the grate and into abutment with the anterior wall of the wedge-shaped housing. The elongate tubular member may further include a reinforced portion at its proximal end to act as a bite block when the wedge-shaped housing is seated within the hypopharynx of a patient. The tubular member is preferably substantially axially rigid and radially flexible to bend to the anatomic contours of the mouth and the pharynx during insertion into and upon being seated in a patient. The housing is preferably flexible and soft to provide some give as the housing is inserted into a patient and rigid enough to prevent collapse of the housing by the epiglottis and tissue surrounding the hypopharynx as the housing is inserted into and seated within a patient. An inflatable cuff is preferably provided around the proximal end of the wedge-shaped housing or the elongate tubular member proximate the proximal end of the wedge-shaped housing. A temperature sensor may be provided on the housing or on the inflatable cuff. An adaptor for facilitating fluid tight connection of the proximal end of the elongate tubular member to a respiratory circuit or an anesthesia circuit can be permanently or releasably attached to the proximal end of the elongate tubular member.
In another embodiment of the grated oral airway the grate is connected to the anterior wall of the housing by a hinge so that the grate is pivotable to uncover the leading opening. In this embodiment, the tubular member preferably extends within the housing and is positioned therein to direct an instrument inserted in the tubular member anteriorly, whereby with the wedge-shaped housing positioned adjacent to a patient""s glottis, the instrument is directed toward the trachea as it is axially advanced within the elongate tubular member.
In yet another embodiment of the grated oral airway the grate is made of a flexible material that is rigid enough to slide the epiglottis into abutment with the anterior wall of the wedge-shaped housing as the wedge-shaped housing is inserted into the hypopharynx and flexible enough to enable an endotracheal tube or other instrument to be axially driven between a gap defined by the grate by displacing the flexible grate material defining the gap. The grate preferably consists of a plurality of vertically oriented bars.
Yet another aspect of the present invention is a method of providing the grated oral airway to a patient. The method includes inserting the wedge-shaped housing into the mouth of the patient, axially advancing the wedge-shaped housing to slide the epiglottis over the grate and seating the wedge-shaped housing with a leading surface of the enlarged proximal portion abutting the patient""s aryepiglottic folds, the anterior wall of the wedge-shaped housing abutting the epiglottis and the grate adjacent to the glottis. The method may further include axially inserting an endotracheal tube into the elongate tubular member and deforming the material forming the grate by axially advancing the endotracheal tube through a gap defined by the material forming the grate to locate a distal end of the endotracheal tube in the trachea of a patient, and attaching one of an anesthesia circuit and an airway circuit to a proximal end of the endotracheal tube. The method may further include, after seating the wedge-shaped housing, inflating the inflatable cuff. An anesthesia circuit or another airway circuit can be attached to the distal end of the elongate tubular member following inflation of the cuff.
Yet another aspect of the present invention is an elongate tubular member having a distal and a proximal end, the distal end having an opening that is inclined so that a posterior portion of the distal end extends beyond an anterior portion of the distal end. A grate covers the leading opening, the grate being configured so that as a patient""s epiglottis is engaged by the grate during insertion of the distal end into the hypopharynx, the epiglottis slides up the grate and into abutment with an anterior portion of the tubular member.
The present invention provides an oral airway for reliably holding soft tissue structures away from the laryngeal opening to assure adequate airflow to a patient. The invention also provides a supraglottic airway which holds soft tissues in the vicinity of the laryngeal opening apart and which provides for seating of the distal end of the oral airway in a consistent and precise manner adjacent the larynx or glottis aperture for facilitating positive pressure ventilation by anesthesia circuit, resuscitation mask or ventilator. Furthermore, those embodiments providing either a flexible grate or a pivoting grate allow for reliable blind passage of an endotracheal tube into the trachea. These many advantages are provided by a structure which is rigid enough to assure proper placement and to prevent inadvertent kinking of the airway, yet soft enough to minimize the risk of injury to the sensitive tissue of the oral cavity, pharynx and hypopharynx. The present invention further includes embodiments to prevent occlusion of the breathing tube by a patient""s teeth. Those embodiments with a temperature monitor allow for monitoring of the body temperature to guard against hypothermia and as an early warning of possible maligmant hyperthermia. The flexible breathing tube can be manipulated by an operating surgeon to remove it from the operating theater within an oral cavity or pharynx. Finally, all these many advantages are provided by an airway which is relatively easily manufactured from inexpensive materials, thereby promoting its widespread use and making its many advantages readily available.